1. Field of the Invention
The present invention relates generally to an inking device for supplying ink that is fed to an ink rail to a printing plate on a plate cylinder via a group of roller that are sequentially in contact with each other, and more particularly to an inking device in which ink droplets and ink particles produced from a relatively thick ink film transferred from the ink rail to the first roller are prevented from scattering to the outside of the printing press.
2. Description of the Prior Art
It is well known that an ink film is often reduced to filaments in between rotating rollers while a printing press is in operation, which then break up into multiple ink droplets and particles, and that these droplets and particles repulse each other due to surface static charges and are scattered and suspended in the air.
In a printing operation under the same operating conditions in terms of ink, speed and working environment, it is also known that thicker ink films are more likely to produce ink droplets and particles (refer to xe2x80x9cInsatsu Kogaku Binranxe2x80x9d (Printing Engineering Manual), pp.687xcx9c688, Gihodo Publishing Co., Ltd., 1983.) These ink droplets and particles tend to contaminate printing presses and their surroundings, soil operators"" clothing and aggravate the working environment. They are also likely to contaminate printing paper surface, lowering printing quality.
As a technique to prevent these defects and inconveniences, a technique disclosed in Japanese Published Unexamined Patent Application No. Sho-59(1984)-35945 and Japanese Published Unexamined Utility Model Application No. Sho-61(1986)-81941 is publicly known.
Japanese Published Unexamined Patent Application No. Sho-59(1984)-35945 discloses an inking device having a multitude of ink rollers rotating in contact with each other between an ink feeding section and a plate cylinder, in which ink rollers other than those in the vicinity of the plate cylinder are arranged in such a manner that any one or both of a pair of rollers rotating in contact with each other are disposed in front of the contact area in the rotating direction of another pair of rollers rotating in contact with each other, so that the ink droplets and particles scattered from the contact area of a pair of rollers rotating in contact with each other and suspended in front of both roller in the rotating direction are caused to impinge on those ink rollers provided in front of both rollers in the rotating direction to prevent ink from being scattered and suspended.
Japanese Published Unexamined Utility Model Application No. Sho-61(1986)-81941, on the other hand, discloses an inking device having a group of rollers sequentially coming in contact with each other to feed ink to the plate cylinder, in which high-voltage electrodes are disposed in front of the rollers rotating in contact with each other at predetermined intervals with respect to the contact area of both rollers, with a high voltage source connected to the electrodes so as to apply a high voltage, so that corona discharge is caused to generate by applying a high voltage to form an electrostatic curtain so as to attract the ink droplets and particles scattered and suspended in front of both rollers at the contact area to cause them to redeposit on any of both rollers or accumulate on the electrodes.
There are a number of defects and problems, however, in the techniques disclosed in Japanese Published Unexamined Patent Application No. Sho-59(1984)-35945 and Japanese Published Unexamined Utility Model Application No. Sho-61(1986)-81941, as will be described later.
The technique disclosed in Japanese Published Unexamined Patent Application No. Sho-59(1984)-35945 requires to provide a relatively large number of rollers provided in a limited space, with a roller surrounded on all four sides by other rollers provided to ensure desired operations and effects of the invention. In addition, the technique has poor operability workability since it is extremely difficult to incorporate a mechanism for adjusting roller arrangement and the state of contact of rollers and adjust the state of contact of not only a roller surrounded by other rollers but also some of other rollers by operating the incorporated adjusting mechanism while checking and confirming the state of adjustment. Furthermore, the technique has poor workability since it has some rollers which cannot be changed without disassembling other rollers.
Among ink droplets and particles which are scattered and suspended in various directions as they repulse each other due to surface static charges, those ink droplets and particles that travel toward the outer periphery of the rollers and impinge on the roller outer periphery can be successfully prevented from being scattered and suspended as desired. There are many ink droplets and particles, however, which pass through gaps between rollers due to the aforementioned repulsion force. This makes it difficult to prevent ink droplets and particles from being scattered and suspended.
In the technique disclosed in Japanese Published Unexamined Utility Model Application No. Sho-61(1986)-81941, high-voltage electrodes disposed at predetermined intervals with respect to the contact area in front of rollers rotating in contact with each other at the contact area could interfere with the adjustment of the state of contact between both rollers or the exchange of rollers, posing a workability problem. The electrodes to which a high voltage is applied could attract paper dust with electrostatic attraction, leading to static discharge ignition, presenting fire hazards. Furthermore, the electrodes might be contaminated by the ink droplets and particles passing through the electrostatic curtain and impinging on the electrodes as it is attracted by any force overwhelming the attraction of the electrostatic curtain or by the electrodes of a polarity opposite to that of the static charge. This could necessitate maintenance work to maintain the electrodes in such a clean state as to achieve the desired effects by removing the ink deposited on the electrodes.
In addition to the above, no measures have been available to prevent ink droplets and particles from passing through the electrostatic curtain or the array of electrodes as they are attracted by any force overwhelming the attraction force of the electrostatic curtain or the attraction force exerted by the electrodes of an opposite polarity.
It is therefore an object of the present invention to provide an inking device having a group of rollers sequentially coming in contact with each other to feed ink to a printing plate on a plate cylinder, in which ink droplets and particles that are mostly generated at the contact area of an ink transfer roller to which ink is transferred in a relatively thick film from the ink rail are prevented from being scattered and suspended outside the printing press; the inking device involving no difficulty in arranging rollers and no fire hazards, having good workability and operability, and requiring no special maintenance work.
It is another object of the present invention to provide an inking device which can prevent the ink droplets and particles generated while a printing press is in operation from being scattered and suspended using a simple mechanical arrangement of rollers.
It is a further object of the present invention to provide an inking device which causes the ink droplets and particles generated while a printing press is in operation to deposit on rollers to recirculate them to the inking device.
In the disclosed embodiments, an inking device for feeding the ink fed to the ink rail to a printing plate on a plate cylinder via a group of rollers sequentially coming in contact with each other, comprises a first roller part of the outer periphery of which faces the ink feeding surface of the ink rail, a second roller disposed downstream of the first roller in the ink feeding process and in contact with the outer periphery of the first roller that is downstream side in the rotating direction from the position at which the first roller faces the ink feeding surface of the ink rail, a third roller coming in contact with the first roller on the downstream side in the rotating direction from the position at which the outer periphery of the first roller is in contact with the second roller, and a fourth roller coming in contact with both the outer peripheries of the second and third rollers and blocking the front area in the rotating direction of both rollers at the contact area between the first and second rollers, so that the ink droplets and particles generated in the contact area of both roller are contained in a space enclosed by the first through fourth rollers by the rotation of the first and second rollers.